Ultra-high frequency generating system



June 27, 1933.

A. E. DU MONT 1,915,356

ULTRA-HIGH FREQUENCY GENERATING SYSTEM Original Filed Nov. 26, 1928@nue/mtu Patented `lune 27, 1933 i UNITED STATES PATENT OFFICE A'LL'ENB. DU MONT, OE UPPER MONTGLAIR, NEW JERSEY, AssIGNOR 'ro DE FOREST RADIOCOMPANY, OE PAssAIo, NEW JERSEY, A CORPORATION OE DELAWARE Y ULTRA-HIGHFREQUENCY GENERATING SYSTEM Original application ledrNovemberQG, 1928,Serial No. 321,846'. Divided and this application led March 5, 1930.Serial No. 433,209.

This invention relates to improvements in radio circuits and vacuumdevice therefor.

One of the objects of this invention is the provision of a new form ofelectron discharge device in which the usual plate thereof is I.iliadein the form of a coil of wire and which,

'in conjunction with the gridVV coil, provide the inductively relatedcoils by means of which the plate and grid circuits are associated toprovide a feed back circuit.

A further object of this invention is the provision of an electrondischarge device and circuits therefor which is` particularly adaptedfor the generation of exceedingly short waves.v

A further object of this invention is the 'provision of a short wave orhigh frequency generator and connections therefor whichare `exceedinglysimple and adapted for extreme compactness.

These and other object as Will appear from the following disclosure aresecured by means of this invention.

Referring to the drawing;

Fig. 1 is a diagrammatic illustration of a standard form of transmittingcircuit employing the feed back principle;

Fig. 2 is a diagrammatic illustration of the improved vacuum device ofthis inven- 3o tion and the circuits therefor, whereby ex- "tremely highfrequencies may be generated.

Although this invention is disclosed as applied to a transmittingsystem, it is to be distinctly understood that the principles thereofare applicable to receiving systems, and it is intended that the claimscover both.

One of the diliiculties encountered in producing electron dischargedevices which will oscillate at extremely high frequencies is thecapacity eii'ect of long leads connecting the electrodes of thedevicewith th-e other circuit instrumentalities, and in addition, the eectcaused by the resistance of these leads. In'

producing a vacuum device which will oscillate at a fraction of a wavelength the capacity of these leads and of the electrodes, althoughexceedingly small become of major importance, and in fact, thedetermining factor which limits the frequency at which the device can bemade to oscillate. This invention contemplates the idea of makingtheusual plate and grid electrodes form the primary and secondary ofthetransformer by means of which the output energy in the plate circuit isfed back to the input or grid circuit. By employing these two electrodesfor this purpose it is possible to eliminate the long leads, and infact, any leads at all. This thought is true Where the device is madefor the particular purpose of generating currents of a single highfrequency Where it is not necessary to provide any capacity adjustingmeans to tune the two circuits.r Another highly important advantage ofthis arrangement is that the tube becomes much more sensitive because ofthe combined electrostatic and electro-magnetic control of the electronsby reason of the presence of the currents in the two coil electrodeswithin the vessel. y

A standard transmitting circuit is shown in Fig. 1 for purposes ofcomparison. The oscillating audion is shown with the exhausting vessel 1taking the plate anode 2, grid 3 and filament or cathode el suppliedfrom the current source 5. The anode is connected by wire 6 to oneterminal of the current source 7, the other terminal of which isconnected by wire 8 to the inductance 9. The other terminal of theinductance 9 is connected to one terminal of th-e grid inductance 11which has its other terminal connected to the grid 3 by wire 12. A lead10 connects the cathode circuit to a point between'the iiiductances 9and 11. The antenna circuit is shown Acoinprising the antenna 13connected to one terminal of the inductance 14, the other terminal ofwhich is grounded. The inductances 9 and 11 are closely associated withthe inductances 14. A short circuiting wire including a switch 16 isprovided by means of which a number of turns of the inductance 14 may beshort-circuited upon the closingl of the switch 16 to detune the antennacircuit. An audion circuit of this type provides a source of alternatingcurrent which is sent over the antenna as a continuous wave, thecontinuity of which may periodically interrupted by the closing ofswitch 16 for the purpose of transmitting intelligence. Y

IVhen employing an arrangement of this nature for `the production ofexceedingly high frequencies it is found that the upper limitoffrequency is determined by the capacity inductance and resistancecharacteristics of the leads necess'ary'to conn'ectthe audion device tothe external circuit instrumentalities. To overcome this diiculty it isproposed to make the Vgrid and plate electrodes perform the functionofthe inductances 9 and 11 (Fig. 1).

Referring to Fig. 2 the electron discharge device is shown comprising'anexhausted vessel 17 having the reentrant stem tube 18. The plateelectrode which is usually intheform of a sheet of metal is showninfthis case comprising a coil of wire 21 wound uponthe insulatingvsupports 19 and 20. rThe grid electrode is shown as the usual wirecoil, but in this case, also supported upon insulating supports23 and24.` The insulating supports 20, 24, 23 and 19 are supportedupon wiressecured to the stem tube 18. These insulating supports have beenindicated as secured to the supporting Wires by means ofthe black marksindicating va joint as shown at 20a and 19.. The specific features ofconstruction are of'nor great concern here since they may take anumberof forms. For instance, the insulating supports to extend direct-ly tothe stem tube and be secured therein and then leads .taken off ydirectlyfrom the plate and grid electrodes. The grid electrode 22 p is connectedby the wire 41 to the wire support L11af and the plate electrode 21 isconnected by the wire 25 to the Wire support 25a. The cathode, is .shownat -10 having the leads 31 which connect it to the current source32.

` Supporting wire tlfL is connected to the wire 34, and supporting Wire25a is connected to the'wire26. A Wire 33 extends from the positive sideof the current source 82. and an adjustablecondenseris placed across thewires Stand 88. Wire 26 is connected to the positive side of the currentsourcel 27,. the negative side of which is connected to one-terminal'ofthe inductance 28. Thel other terminal of the inductance 28is'connectedby a Wire 30, to the positive side of the current source 32.Avariable `condenser is connected across the' wires 26 and 80. Theantenna system is shown comprising the antenna 36 and inductan'ce 37which is grounded. As before, a shortcircuiting circuit is provided fora number of turns of the inductance 37 and has a switch 38 therein. Thefeatures of this invention will be at once apparent. Instead ofemploying inductances 9 and 11 by means of which the plate and gridcircuits are associated to provide a feed back of energy the plateelectrode 21 and the grid electrode 22 are employed as these inductancesand are associated with each other within the evacuated vessel. Theinductance 28 is provided as a means through which the oscillatingenergy may be delivered for any use. The condenser 29 is provided totune the plate circuit ofthe device to vary the frequency of the currentgenerated While condenser controls the feed back of energy, but it is atonce apparent'thatwhen the device ismade to generateone frequency onlythese condensers can be eliminated by d'esigi'iingV the device to havethe proper capacity to generate the. desired frequency. Likewise, othermeans of removing the energy generated may be employed in place of theinductance`28, which could consist of a coil surrounding the tube. toextreme compactness and the few leads that are needed'may readily bereduced to a minimum of length. v4The vacuum device becomes completelywithin itself, with the exception of, the energysource, a 4generator ofhigh frequency currents. It is, of course, apparent-that the;device isnot necessarily limited to extremely high frequencies since lowerfrequencies could be generated thereby.

This device readily lends itself An additional advantage of the deviceis that the currents flowing in the grid `and plate circuits Willflowthrough the grid and plate electrodes -within the vessel and beingclosely associatedwith thercathodeV will aid in the control of theelectrons through electro-static cathode and coiled grid and plateelectrodes l each serving as an open ended inductance, means forlenergizing said cathode, Aa circuit includingone of'fsaid electrodes, asource of energy on said cathodev and a circuit inclu ding the other ofsaid electrodes and said cathode whereby a generator of-y highVfrequency currents is produced in which the two electrodes serve as thesole means for inductively coupling the input and output circuits ofsaid device. 4 Y f 2. In a combination as described, for genly couplingthe input and output circuits.

8. In a combination of the type described for generating ultra highfrequency currents, an evacuated vessel, a cathode within Said vessel,means lfor energizing said cathode, a grid and plate electrode in theform of a wire coil associated with said cathode, an output circuitincluding said plate electrode as an open ended inductance and saidcathode, and an input circuit including said grid electrode as an openended inductance and said cathode whereby the plate and grid electrodesserving as the lsole means to induc- A tively couple the input andoutput circuits.

4. In an arrangement for generating ultra high frequency currents, the.combination comprising an exhausted vessel, a cathode, an inductivelyvwound'grid and an inductively wound anode within said vessel, an outputcircuit connectedbetween said anode and cathode, anV input circuitconnected between said grid and cathode, including said grid as an openended inductance, and means for tuning said input and output circuits,said grid and anode acting as means for inductively coupling the inputand output circuits.

' 5. Means for generating ultra highy frequencies comprising an electronemitting cathode, an anode in the form of a coil having its individualturns insulatingly spaced apart, a control grid in the formV of a coilhaving its individual turns insulatingly spaced apart, circuitconnections for connecting only one end of said grid to said cathodewhereby said grid operates as an open ended inductance, and means forconnecting said anode to said -cathode in inductive relation to saidgrid.

6. Means for generating ultra high frequencies comprising an electronemitting cathode, an anode in the form of a coil having the individualturns insulatingly spaced apart, a control grid in the form of a coilhaving the individual turns insulatingly spaced apart, circuitconnections for connecting only one end of said anode to said cathode,whereby said anode operates as an open ended inductance, and meansconnecting said grid to said cathode in inductive relation to saidanode.

7. Means for generating ultra high frehaving the individual turnsinsulatingly spaced apart, a connection from one end of said anode tosaid cathode whereby said anode operates as an open ended inductance,said grid and anode being mounted in inductive relation. c

In testimony whereof I have hereunto set apart, a control grid in theform of a coil y my hand on'this 25th day of February, A.

ALLEN B. DU MONT.

